| TAO Jing,MA Weiwei,ZHU Maoxu,LI Tie,YANG Rujun. 2017. Characterization of iron diagenesis in marine sediments using refined iron speciation and quantized iron(Ⅲ)-oxide reactivity: a case study in the Jiaozhou Bay, China. Acta Oceanologica Sinica, 36(7):48－55 |
| Characterization of iron diagenesis in marine sediments using refined iron speciation and quantized iron(Ⅲ)-oxide reactivity: a case study in the Jiaozhou Bay, China |
| 用细化的铁形态分析及量化的铁氧化物活性表征海洋沉积物中铁的成岩作用：以胶州湾为例 |
| Received:April 21, 2016 Revised:December 02, 2016 |
| DOI：10.1007/s13131-016-1083-2 |
| Key words:iron oxides Jiaozhou Bay in China marine sediments microbial iron reduction reactivity speciation |
| 中文关键词: 铁氧化物 胶州湾 海洋沉积物 铁微生物还原 活性 形态 |
| 基金项目:The National Natural Science Foundation of China under contract Nos 41576078 and 41276069; the Shandong Province Natural Science Foundation of China under contract No. ZR2015DM006; the National Key Research and Development Program of China under contract No. 2016YFA0601301. |
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| Abstract: |
| As a case study, refined iron (Fe) speciation and quantitative characterization of the reductive reactivity of Fe (Ⅲ) oxides are combined to investigate Fe diagenetic processes in a core sediment from the eutrophic Jiaozhou Bay. The results show that a combination of the two methods can trace Fe transformation in more detail and offer nuanced information on Fe diagenesis from multiple perspectives. This methodology may be used to enhance our understanding of the complex biogeochemical cycling of Fe and sulfur in other studies. Microbial iron reduction (MIR) plays an important role in Fe(Ⅲ) reduction over the upper sediments, while a chemical reduction by reaction with dissolved sulfide is the main process at a deeper (> 12 cm) layer. The most bioavailable amorphous Fe(Ⅲ) oxides [Fe(Ⅲ)am] are the main source of the MIR, followed by poorly crystalline Fe(Ⅲ) oxides [Fe(Ⅲ)pc)] and magnetite. Well crystalline Fe(Ⅲ) oxides [Fe (Ⅲ)wc] have barely participated in Fe diagenesis. The importance of the MIR over the upper layer may be a combined result of the high availability of highly reactive Fe oxides and low availability of labile organic matter, and the latter is also the ultimate factor limiting sulfate reduction and sulfide accumulation in the sediments. Microbially reducible Fe(Ⅲ) [MR-Fe(Ⅲ)], which is quantified by kinetics of Fe(Ⅱ)-oxide reduction, mainly consists of the most reactive Fe(Ⅲ)am and less reactive Fe(Ⅲ)pc. The bulk reactivity of the MR-Fe(Ⅲ) pool is equivalent to aged ferrihydrite, and shows down-core decrease due to preferential reduction of highly reactive phases of Fe oxides. |
| 中文摘要: |
| 以富营养化的胶州湾一个柱状沉积物为例，用细化的铁形态分析及量化的铁氧化物还原活性相结合的方法研究了沉积物中铁的成岩作用过程。结果表明，这两种方法相结合的结果能更详细示踪铁的转化并能从多视角提供铁成岩作用的细微差别。这一方法有望应用于其它研究中更好地揭示复杂的铁和硫的生物地球化学循环。铁微生物还原在上部沉积物铁的还原中起重要作用，但12 cm深度以下铁被硫化物的化学还原为主要过程。最具生物活性的无定形铁氧化物是铁微生物还原的主要参与者，然后依次为弱晶态铁氧化物和磁铁矿，晶态铁氧化物几乎不参与铁的成岩循环。沉积物上部铁微生物还原的重要作用主要是活性铁含量高而活性有机质含量低共同作用的结果，且后者也是沉积物中硫酸盐还原速率以及硫化物积累的最终制约因素。对比研究表明，通过还原性溶解动力学方法表征的微生物可还原的铁氧化物主要由无定形和弱晶态铁氧化物组成，其总体活性常数相当于老化的水铁矿，且随深度增加而减低。 |
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